The posts which support signs, lights, etc. by the sides of highways have been determined to be hazards to automobiles which leave the paved portion of the highways. Eliminating the hazards by eliminating the posts is not possible, since the posts support items that are necessary to the use of the highway (i.e., lights at intersections, exit instructions, route number, etc.). Therefore the posts are designed to break readily under impact by a car, thereby allowing the car to roll to a controlled stop rather than crash into a rigid, unyielding post.
In the case of a post that supports a sign, however, wind loading on the sign presents a problem. A low wind pressure, acting on a large sign area, puts a substantial amount of stress on the support posts. If conventional posts are designed to break under impact by a car, it is possible that the wind loading will generate enough force to break the posts. Conversely, designing the posts to withstand the wind loading makes them too strong to break except under very high speed impacts; for low speed impacts they act as rigid barriers, and are the source of crash damage to the car and its occupants.
Accordingly, it is an object of the present invention to provide a support post for a sign that will break easily under the impact of a car but which will be impervious to wind loading.
It is a further object to provide such a post that can be easily and inexpensively repaired after impact.